Process for manufacturing a turbine or compressor wheel made of composite material and wheel thus obtained

ABSTRACT

This invention relates to a process for manufacturing a turbine or compressor wheel made of composite material, comprising the following steps of: 
     making at least two helicoidal textures each formed by weaving a spiral band with helicoidal warp yarns and weft yarns which are substantially perpendicular to the axis of the texture, 
     assembling the helicoidal textures by &#34;screwing&#34; them in each other and stacking them by mutually approaching their interlaced turns, and 
     densifying the stack thus made to obtain a preform of a turbine or compressor wheel.

The present invention relates to a turbine or compressor wheel made ofcomposite material.

The use of composite materials for manufacturing turbo-machine partsnecessitates using fibrous reinforcement having high mechanicalcharacteristics. The nature of the fibers constituting the reinforcementis selected as a function of the chemical and thermal conditions of theenvironment in which the parts are to be used. The orientation anddistribution of the fibers are determined as a function of thethermo-mechanical stresses.

It is an object of the invention to provide a process for obtaining, atan advantageous cost, fibrous reinforcing structures which areparticularly well adapted to making wheels of turbines or compressors.

This purpose is attained by a process comprising, in accordance with theinvention, the following steps of:

making at least two helicoidal textures each formed by weaving a spiralband with helicoidal warp yarns and weft yarns which are substantiallyperpendicular to the axis of the texture,

assembling the helicoidal textures by "screwing" them in each other andstacking them by mutually approaching their interlaced turns, and

densifying the stack thus made to obtain a preform of a turbine orcompressor wheel.

The spiral weave textures are particularly well adapted to making piecesused in rotation in which the mechanical efforts generate stressesessentially in circumferential traction and in radial traction.

Furthermore, the stacking of a plurality of textures makes it possible,by an appropriate choice of the dimensions of such textures, to producewheel preforms of thickness varying from the small diameter, in thevicinity of the hub, up to the periphery. For example, the stacking of aplurality of textures of the same small diameter but of different largediameters allows the production of preforms of thickness decreasing fromthe vicinity of the hub up to the periphery. Such preforms are thereforeparticularly well adapted to the production of wheels of turbines orcompressors. Final manufacture of the preform by machining isfacilitated and, in particular, a very important saving of material ismade in comparison with the use of cylindrical preforms of constantthickness.

The invention also relates to a turbine or compressor wheel as obtainedby carrying out the process defined hereinbefore.

The turbine or compressor wheel made of composite material is, accordingto the invention, characterized in that it comprises a reinforcingstructure formed by the stacking of a plurality of helicoidal textures"screwed" one in the other, each texture being formed by a spirallywoven band with helicoidal warp yarns and weft yarns substantiallyperpendicular to the axis of the texture.

The invention will be more readily understood on reading the followingdescription with reference to the accompanying drawings, in which:

FIG. 1 is a view in perspective showing two helicoidal textures intendedfor making a turbine wheel according to the invention.

FIG. 2 is a view in perspective illustrating the assembly of thetextures of FIG. 1.

FIG. 3 is a schematic view in section showing the textures of FIG. 1assembled and stacked in a tool for densification, and

FIG. 4 is a schematic view in section showing the preform obtained afterdensification in the tool of FIG. 3.

FIG. 5 is an elevation of the body shown in FIG. 2 in the condition itassumes when the turns of the body are brought clsoe together byapplying a compressive force in the direction of the axis of the body.

FIG. 6 is an elevation showing the configuration of the body when aforming die of the type shown in FIG. 3 is employed.

Referring now to the drawings, the two textures 10 and 11 of FIG. 1 areconstituted by fibrous reinforcing bands, each band having a surfacegenerated by a segment of which the vertices describe two coaxialhelices of the same pitch and which extends in a direction substantiallyperpendicular to the axis of these helices.

The helicoidal textures 10 and 11 are made by spiral weaving withhelicoidal warp yarns and weft yarns perpendicular to the axis of thetexture. This mode of weaving has been known for a long time. Referencemay be made for example to French Patent No. 646 341 of Dec. 24, 1926.

The yarns used are for example yarns formed by fibers of carbon, siliconcarbide, alumina, Kevlar, or yarns based on other fibers having highmechanical and/or thermal characteristics. Weaving may be of the cloth,satin or other type.

Textures 10 and 11 present the same inner diameter d, but differentouter diameters D1 and D2, the and forming texture 10 being wider thanthe one forming texture 11.

The two textures 10 and 11 are assembled with the same pitch by"screwing" one of the textures in the other. In this way, each turn ofone texture is intercalated between two turns of the other texture (FIG.2).

After assembly, the textures are stacked. Texture 11 having an outerdiameter smaller than that of texture 10, an excess thickness may thusbe obtained in the part adjacent the smaller diameter, i.e. in that partintended to form the hub of the wheel.

With a view to densification of the reinforcing structure, the latter isplaced in a tool maintaining the textures 10 and 11 stacked. As shown inFIG. 3, this tool is constituted essentially by a mould of which theannular cavity 12 presents, in cross-section, a first part whose widthdecreases from the small diameter in the direction of the periphery anda second part of constant width which joins the first part and extendsradially up to the large diameter.

As is known per se, densification consists in infiltrating a matrixwithin the porosity of the reinforcing structure. The matrix is forexample made of refractory material such as carbon or silicon carbide.Infiltration is effected for example by chemical vapor deposition or byliquid impregnation followed by a heat treatment.

After densification, the preform 13 obtained (FIG. 4) is machined toform the desired wheel; the blades of the wheel are made by machiningthe peripheral part of the preform. The use of a plurality of helicoidaltextures of different dimensions enables a preform to be obtained whichis similar to the shape of the final piece; there is therefore a verysubstantial saving of material.

In certain cases, it is advantageous to weave at least one of thehelicoidal textures with a weight per square meter which varies betweenthe small diameter and the large diameter. For example, by increasingthe density of helicoidal warp yarns on the small diameter side, apreform is obtained with a circumferential reinforcement rate highernear the hub than near the periphery.

Other modifications and additions may be made to the embodimentdescribed hereinbefore without departing from the scope of protection asdefined by the accompanying claims. In particular, the number ofhelicoidal textures used may be greater than two.

What is claimed is:
 1. A process for manufacturing a turbine orcompressor wheel made of composite material, said process comprising thefollowing steps of:making at least two helicoidal textures each formedby weaving a spiral band with helicoidal warp yarns and weft yarns whichare substantially perpendicular to the axis of the texture, assemblingthe helicoidal textures by "screwing" them in each other and stackingthem by mutually approaching their interlaced turns, and densifying thestack thus made to obtain a preform of a turbine or compressor wheel. 2.The process of claim 1, wherein helicoidal textures formed by bands ofdifferent widths are assembled.
 3. The process of claim 2 wherein atleast one of the textures is woven with a variable weight per squaremeter so as to obtain a variable reinforcement rate within the preform4. The process of claim 1 wherein at least one of the textures is wovenwith a variable weight per square meter so as to obtain a variablereinforcement rate within the preform.